Recently, there has been a great interest in understanding the physical principles of the locomotion mechanisms of microswimmers.
Important examples are biological microorganisms such as bacteria, sperm cells or algae, and artificial self-propelled swimmers such as active colloids [1]}, [2]} or active emulsion droplets [3]}.
Their
locomotion is mainly governed by low Reynolds number hydrodynamics and thermal or biological noise.
While swimming speed and flow fields of a single noiseless microswimmer in
a
bulk
fluid may be calculated analytically
in some simple cases by solving
Stokes equations [4]}, [5]}, [6]}, [7]}, [8]},
analytical methods are less suitable for swimmers in complex environments,
in the presence of other swimmers, or when Brownian fluctuations become important.
Hence several numerical methods are used nowadays to overcome these limitations.
Very succesful tools are coarse-grained hydrodynamic simulation methods such as
lattice Boltzmann (LB), dissipative particle dynamics (DPD),
and multiparticle collision dynamics (MPCD) –
a special version of which is
stochastic rotation dynamics (SRD).
These methods allow to simulate the
time evolution
of one or many swimmers, in bulk as well as in confinement.
While MPCD and DPD are particle-based methods and naturally include thermal fluctuations, LB is based on the time
evolution of smooth velocity
distribution functions
and noise may be included on top.
